Lauren Cohan, Mark O’Brien & Mia Tomlinson Join Prime Video’s ‘Stillwater’ As Series Regulars

Prime Video‘s Stillwater has set three for series regular roles opposite lead Ben Hardy: Lauren Cohan (The Walking Dead), Mark O’Brien (The Copenhagen Test), and Mia Tomlinson (The Conjuring: Last Rites).

Hailing from Warner Bros. Television, Berlanti Productions and Skybound Entertainment, Stillwater adapts the Skybound graphic novel by Chip Zdarsky and Ramón K Pérez. The show is a horror thriller revolving around Hardy’s ex-con, Daniel West. When Daniel receives a mysterious letter promising answers about his past and a substantial inheritance in the small town of Stillwater, he discovers a community where nothing ever ages, no one ever dies, and nobody ever gets out.

Cohan plays Catherine ‘Cat’ Keegan, a former homecoming queen whose small-town charm has sharpened into something fiercer thanks to decades of old grudges and regrets. Deeply loyal to her husband Ted, a sheriff’s deputy played by O’Brien, Cat has spent years convincing herself that the things they do to protect the town’s secret are justified.

O’Brien’s Ted Keegan is a father, farmer and military veteran — a hardened man who’s spent much of his life following orders and keeping secrets. As a deputy in Stillwater, he enforces the town’s strict policies, sometimes through violent means, all while hiding a truth that could destroy his own family.

Tomlinson plays Cat’s younger sister, Laura Quinn, a spirited single mother with a stubborn streak who had her hands full long before the people of Stillwater suddenly stopped aging or dying. When her hometown changed overnight, Laura faced an impossible choice that would alter her future — and the town as a whole — forever.

Stillwater is being shepherded by executive producers Greg Berlanti and Carly Wray, who co-wrote the pilot episode. The eight-episode series was ordered ahead of San Diego Comic-Con in July 2026.

Other executive producers on the series include Sarah Schechter, Leigh London Redman, and Robbie Rogers via Berlanti Productions and its overall deal with WBTV; Robert Kirkman, David Alpert, Rick Jacobs, Glenn Geller, and Zdarsky via Skybound Entertainment; and Jonathan Gabay.

New series regular Cohan is known for her role as Maggie Greene on AMC’s smash zombie series The Walking Dead and spin-off The Walking Dead: Dead City, on which she’s an executive producer. Next up, she’ll be seen starring in Todd Flaherty’s film Boys Like Daniel, opposite Matt Bomer, and Eric Stoltz’s rom-com Embers, opposite Jake Epstein. The British-American actress is repped by Anonymous Content, CAA, and Hansen Jacobson Teller.

O’Brien has most recently been seen in Peacock’s The Copenhagen Test and the critically acclaimed WWII drama Nuremberg. Upcoming, he has the Netflix thriller Trinity created by Jed Mercurio, Warner Bros.’ action thriller F.A.S.T. written by Taylor Sheridan, and the dark comedy Little One produced by Zach Cregger and Roy Lee. He is repped by UTA, Thruline Entertainment, Lichter, Grossman, Nichols, and The Characters Talent Agency.

For British actress Tomlinson, Stillwater marks a reunion with Hardy following Warner Bros.’ The Conjuring: Last Rites, where she played Judy, the daughter of paranormal investigators Ed and Lorraine Warren. She is repped by UTA, Julian Belfrage Associates, and Peikoff Mahan.